It won't cause any kind of problem that would be of major concern like blowing up the front speaker or increasing global warming or anything like that.
The crawl test is very effective for determining the best location for the sub but then the real world steps in to bash your hopes and dreams (ok, well it's not that bad...)
If you can feasibly place the sub in the location that is likely best then do it; if not, find the next best place. We all have to work against multiple factors like room shape, size, aesthetic concerns, etc. There are other ways to work around small issues if the placement is not 'ideal'.